A kinetic study of catalytic hydrothermal reactions of acetaldehyde with cubic CeO₂ nanoparticles

The hydrothermal reactions of acetaldehyde using cubic CeO₂ nanoparticles were performed on the assumption that repolymerisation of monolignin by aldehydes can be suppressed by catalytic oxidation in the presence of CeO₂ during depolymerisation of lignin. The catalytic potential of cubic CeO₂ nanoparticles was evaluated by comparing them with octahedral CeO₂ via their structural, morphological, catalytic characterisation and in terms of catalytic reactivity. In the cubic CeO₂ system, the conversion of acetaldehyde and the selectivity of acetic acid (oxidation of acetaldehyde) were higher than those in octahedral CeO₂, while the selectivity of crotonaldehyde produced by aldol condensation was lower than that in octahedral CeO₂. The overall reaction mechanism was also developed based on a kinetic study on the primary products of acetaldehyde using the first-rank Delplot method. According to its catalytic oxidation rate constant, cubic CeO₂ has 3–5 times higher oxidative catalytic potential than octahedral CeO₂, suggesting that the repolymerisation of monolignin by aldehydes can be effectively suppressed by cubic CeO₂ nanocatalysts.